The number of Americans who suffer from mild-to-moderate chronic renal insufficiency (CRI) is estimated to be over 10 million and growing. However, remarkably little is known about epidemiology, care, and outcomes of patients with CRI. Furthermore, the predictors of progression to end-stage renal disease and the impact of CRI on the risk of cardiovascular and peripheral vascular disease are not well understood. We propose to establish a joint San Francisco Bay Area Clinical Center between Kaiser Permanente of Northern California and the University of California, San Francisco to contribute to the NIDDK-sponsored cohort of 3000 patients with mild-to-moderate CRI. We will enroll 520 subjects: 410 from Kaiser Permanente and 110 subjects from the University of California, San Francisco as well as provide a unique, large automated matched cohort of adults from Kaiser with preserved renal function. The specific aims of the study are: Aim 1: To characterize the progression of renal insufficiency in ambulatory patients and to identify predictors of rapid deterioration of renal function. Aim 2: To determine how the risk of cardiovascular, cerebrovascular, and peripheral vascular events is associated with the severity of renal insufficiency and how its relationship is affected by "traditional" and "novel" vascular risk factors in different patient subgroups. Aim 3: To assess the variation in the access and quality of care for patients with chronic renal insufficiency across sociodemographic subgroups, geographic areas, and health systems and its association with clinical outcomes Aim 4: To evaluate the clinical and prognostic utility of measured glomerular filtration rate normalized to body surface area compared to serum creatinine, estimated or measured creatinine clearance, estimated glomerular filtration rate and measured absolute glomerular filtration rate across different demographic and disease subgroups.